Fiber-based artificial muscles are promising for smart textiles capable of sensing, interacting, and adapting to environmental stimuli. However, the application of current artificial muscle-based textiles in wearable and engineering fields has largely remained a constraint due to the limited deformation, restrictive stimulation, and uncomfortable. Here, dual-responsive yarn muscles with high contractile actuation force are fabricated by incorporating a very small fraction (<1 wt.%) of Ti3C2Tx MXene/cellulose nanofibers (CNF) composites into self-plied and twisted wool yarns. They can lift and lower a load exceeding 3400 times their own weight when stimulated by moisture and photothermal. Furthermore, the yarn muscles are coiled homochirally or heterochirally to produce spring-like muscles, which generated over 550% elongation or 83% contraction under the photothermal stimulation. The actuation mechanism, involving photothermal/moisture-mechanical energy conversion, is clarified by a combination of experiments and finite element simulations. Specifically, MXene/CNF composites serve as both photothermal and hygroscopic agents to accelerate water evaporation under near-infrared (NIR) light and moisture absorption from ambient air. Due to their low-cost facile fabrication, large scalable dimensions, and robust strength coupled with dual responsiveness, these soft actuators are attractive for intelligent textiles and devices such as self-adaptive textiles, soft robotics, and wearable information encryption.

Researcher/Author: 

NUS – Prof Pooi See Lee
NTU – Dr Liuxiang Zhan, Dr Shaohua Chen, Dr Yangyang Xin, Dr Jian Lv, Dr Hongbo Fu, Dr Dace Gao, Dr Feng Jiang, Dr Xinran Zhou, Dr Ni Wang,

Published in:  Advanced Science (22 April 2024)

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DOI:  https://doi.org/10.1002/advs.202402196

Fiber-based artificial muscles are promising for smart textiles capable of sensing, interacting, and adapting to environmental stimuli. However, the application of current artificial muscle-based textiles in wearable and engineering fields has largely remained a constraint due to the limited deformation, restrictive stimulation, and uncomfortable. Here, dual-responsive yarn muscles with high contractile actuation force are fabricated by incorporating a very small fraction (<1 wt.%) of Ti3C2Tx MXene/cellulose nanofibers (CNF) composites into self-plied and twisted wool yarns. They can lift and lower a load exceeding 3400 times their own weight when stimulated by moisture and photothermal. Furthermore, the yarn muscles are coiled homochirally or heterochirally to produce spring-like muscles, which generated over 550% elongation or 83% contraction under the photothermal stimulation. The actuation mechanism, involving photothermal/moisture-mechanical energy conversion, is clarified by a combination of experiments and finite element simulations. Specifically, MXene/CNF composites serve as both photothermal and hygroscopic agents to accelerate water evaporation under near-infrared (NIR) light and moisture absorption from ambient air. Due to their low-cost facile fabrication, large scalable dimensions, and robust strength coupled with dual responsiveness, these soft actuators are attractive for intelligent textiles and devices such as self-adaptive textiles, soft robotics, and wearable information encryption.

Researcher/Author: 

NUS – Prof Pooi See Lee

NTU – Dr Liuxiang Zhan, Dr Shaohua Chen, Dr Yangyang Xin, Dr Jian Lv, Dr Hongbo Fu, Dr Dace Gao, Dr  Feng Jiang, Dr Xinran Zhou, Dr Ni Wang,

Published in:

Advanced Materials (22 April 2024)

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DOI: 

https://doi.org/10.1002/advs.202402196

The practical application of flexible and stretchable electronics is significantly influenced by their thermal and chemical stability. Elastomer substrates and encapsulation, due to their soft polymer chains and high surface-area-to-volume ratio, are particularly susceptible to high temperatures and flame. Excessive heat poses a severe threat of damage and
decomposition to these elastomers. By leveraging water as a high enthalpy dissipating agent, here, a hydrogel encapsulation strategy is proposed to enhance the flame retardancy and thermal stability of stretchable electronics.
The hydrogel-based encapsulation provides thermal protection against flames for more than 10 s through the evaporation of water. Further, the stretchability and functions automatically recover by absorbing air moisture. The incorporation of hydrogel encapsulation enables stretchable electronics to maintain their functions and perform complex tasks, such as fire saving in
soft robotics and integrated electronics sensing. With high enthalpy heat dissipation, encapsulated soft electronic devices are effectively shielded and retain their full functionality. This strategy offers a universal method for flame retardant encapsulation of stretchable electronic devices.

Researcher/Author: 

Can Cao, Shaobo Ji, Ying Jiang, Jiangtao Su, Huarong Xia, Haicheng Li, Changhao Tian,
Yi Jing Wong, Xue Feng, and Xiaodong Chen

Published in: Advanced Materials, 10 April 2024

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DOI: https://doi.org/10.1002/adma.202401875

A new family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides (MXenes) has attracted increasing attention owing to their electrical, chemical, and physical properties. Together with various attractive properties of the MXenes, they also exhibit electrochemical induced deformation (i.e., expansion/contraction) via ion intercalation/de-intercalation in/from MXene layers.

In this respect, MXenes offer the possibility of application as the electrode of electrochemical actuators (ECAs). While the MXene-based ECAs are still in their infancy stage, researchers have made great effort to achieve high-performance MXene-based electrochemical capacitors (ECs). As the name suggests, both ECAs and ECs shared common traits in which their operations are based on electrochemical processes. This review provides the recent progress in the MXene-based ECAs in parallel with that in the MXene-based ECs to gain insights from the relatively mature developments in EC applications.

Finally, based on the findings from previous studies on both electrochemical applications, perspectives on future MXene-based ECAs in terms of electrode, electrolyte, and cell configuration are provided.

Researcher/Author: 

Dr Jinwoo Park, Dr Younghoon Kim, Dr Hyunwoo Bark and Prof Pooi See Lee

Published in:  Small Structures on 4 Apr 2024

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DOI : https://doi.org/10.1002/sstr.202300520

The calibration and characterization of phased arrays usually requires the separate characterization of the antenna
array and the RF circuitry. A method is presented to characterize them combined in one step for the case of a receiving phased array, as the beamforming algorithm only requires the combined characterization. The characterization results are directly used in the computation of the digital beamforming weights. The method is applied to an L band phased array with eight elements using the Xilinx radio frequency system on chip (RFSoC).

Researcher/Author: 

Peizhuo Yang, Jiahao Wang, Koen Mouthaan

Published in: https://ieeexplore.ieee.org/xpl/conhome/10460592/proceeding

Added to IEEE Xplore: 13 March 2024

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DOI: https://doi.org/10.1109/ARFTG59840.2024.10460741

Position estimation of the antenna elements of a deformed array using received signals is presented. The model considers a uniform linear array (ULA) with a change in the positions of the elements due to deformation of the array. Multiple sources with known direction of arrival (DOA) are used to estimate the position of each antenna element within a certain range. The proposed estimation technique is demonstrated for a deformed array with eight elements under the noiseless and noisy condition.

Researcher/Author: 

Jiahao Wang and Koen Mouthaan

Published in:

2023 IEEE International Symposium On Antennas And Propagation (ISAP)

Added to IEEE Xplore, 22 Jan 2024

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DOI: 10.1109/ISAP57493.2023.10388675

Thermal safety issues of batteries have hindered their large-scale applications. Non-flammable electrolytes improved safety but solvent evaporation above 100 ºC limited thermal tolerance, lacking reliability. Herein, fire-tolerant metal-air batteries were realized by introducing solute-in-air electrolytes whose hygroscopic solutes could spontaneously reabsorb the evaporated water solvent. Using Zn/CaCl2-in-air/carbon batteries as a proof-of-concept, they failed upon burning at 631.8 ºC but self-recovered then by reabsorbing water from the air at room temperature. Different from conventional aqueous electrolytes whose irreversible thermal transformation is determined by the boiling points of solvents, solute-in-air electrolytes make this transformation determined by the much higher decomposition temperature of solutes. It was found that stronger intramolecular bonds instead of intermolecular (van der Waals) interactions were strongly correlated to ultra-high tolerance temperatures of our solute-in-air electrolytes, inspiring a concept of non-van der Waals electrolytes. Our study would improve the understanding of the thermal properties of electrolytes, guide the design of solute-in-air electrolytes, and enhance battery safety.

Researcher/Author: 

Huarong Xia, Shengkai Cao, Zhisheng Lv, Jiaqi Wei, Song Yuan, Xue Feng, and Xiaodong Chen

Published in: Angew. Chem. Int. Ed. 2024, e202318369

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https://doi.org/10.1002/anie.202318369